Insulin and other injectable medications are commonly given with drug delivery pens, whereby a disposable pen needle is attached to facilitate drug container access and allow fluid egress from the container through the needle into the patient.
As technology and competition advance, driving the desire for shorter, thinner, less painful, and more efficacious injections, the design of the pen needle and parts thereof becomes more and more important. Designs need to proactively address ergonomically improving injection technique, injection depth control and accuracy, the ability to be safely used and transported to disposal, and protection against misuse while maintaining the ability to be economically manufactured on a mass production scale.
Drug delivery pens, such as the existing drug delivery pen 100 shown in FIGS. 1 and 2, typically comprise a dose knob/button 24, an outer sleeve 13, and a cap 21. The dose knob/button 24 allows a user to set the dosage of medication to be injected. The outer sleeve 13 is gripped by the user when injecting medication. The cap 21 is used by the user to securely hold the pen injector device 100 in a shirt pocket, purse or other suitable location and provide cover/protection from accidental needle injury.
FIG. 2 is an exploded view of the pen needle assembly 100 of FIG. 1. The dose knob/button 24 has a dual purpose and is used both to set the dosage of the medication to be injected and to inject the dosed medicament via the lead screw 7 and stopper 15 through the medicament cartridge 12 attached through the reservoir housing or hub 20. In standard drug delivery pens the dosing and delivery mechanisms are all found within the outer sleeve 13 and are not described in greater detail here as they are understood by those knowledgeable of the prior art. The medicament cartridge 12 is typically attached to a standard pen injector housing via known attachment means, such as ¼ turn fastening features. The distal movement of the plunger or stopper 15 within the medicament cartridge 12 causes medication to be forced into the reservoir housing 20. The medicament cartridge 12 is sealed by septum 16, which is punctured by a septum penetrating needle cannula (not shown) located within reservoir housing 20. Reservoir housing 20 is preferably screwed onto the medicament cartridge 12, although other attachment means can be used. To protect the patient needle 11, an outer shield 69 attaches to the pen needle assembly 9. An inner shield 59 covers the patient needle 11 within the outer shield 69. The cap 21 fits snugly against outer sleeve 13 to allow a user to securely carry the drug delivery pen 100.
Another existing pen needle assembly 2 is shown in FIG. 3. The needle assembly 2 includes a cover 101, an inner shield 200, a needle cannula 300, and a needle hub 400. A proximal end 310 of the needle cannula 300 is inserted into a center opening in the distal (patient) end 405 of the needle hub 400 until a predetermined length of the distal end 305 of the needle cannula 300 remains extended. The needle cannula 300 is secured by epoxy or adhesive in the distal end 405 of the hub 400 within the hub protrusion 420.
To protect users from injury and the needle cannula 300 from being damaged, the inner shield 200 covers the exposed portion of needle cannula 300. The open proximal end 210 of the inner shield 200 is placed over the exposed portion of needle cannula 300. The open proximal end 110 of the cover 100 envelops the inner shield 200, needle cannula 300, and hub 400.
Distal end 105 of the cover 101 is closed to prevent contamination and damage to the inner components of pen needle assembly 2, and to prevent injury to anyone who may handle it prior to use. The proximal end 410 of the hub 400 is typically covered by a sanitary cover (not shown) on end 110 of cover 101. The pen needle assembly 2 is then ready for shipment to a user. When the user is ready to use the pen needle assembly 2, the sanitary cover (not shown) is removed, the hub 400 is screwed onto a standard medication cartridge 12 (FIG. 2), and the cover 101 and inner shield 200 are separately removed from the hub 400/cannula 300 subassembly by a pulling action. The distal end 205 of the inner shield 200 is closed to cover the distal end 305 of the needle cannula 300 after the cover 101 is removed to protect the user from an accidental stick. The inner shield 200 is then removed to access the needle cannula 300. Thus, two separate pulling actions are required to remove both the cover 101 and the inner shield 200.
FIG. 4 is a cross-sectional view of a pen needle assembly in the configuration that it would be received by a user (with a sanitary cover not shown). An inner shield 470 covers a needle cannula 430. Additionally, the hub 460 includes a center hub protrusion 465. The skin contact plane 450 is the plane of the straight surface across the distal end of the center hub protrusion 465.
A protrusion 520, in which the cannula is bonded, extending from the hub 500 of existing pen needle assemblies is typically narrow, as shown in FIG. 5. The small surface area 530 provided at the distal end of a narrow hub protrusion 520 results in a high pressure being exerted against a patient's skin during injection of the cannula, thereby increasing discomfort of the patient.
Furthermore, the bonding adhesive used to bond the cannula to the hub is typically disposed within the hub protrusion. The adhesive is cured by exposure to ultraviolet (UV) radiation or by application of heat or chemical reaction from a two-part adhesive. Because the adhesive is within the hub protrusion, the UV radiation must pass through the hub walls, which are typically made of polypropylene, to induce curing in the adhesive. Thus, a lengthy curing time is required to cure the adhesive due to the UV radiation having to pass through the hub walls to irradiate the adhesive.
Drug delivery pens are also disclosed in U.S. Patent Application Publication Nos. 2006/0229562 to Marsh et al. and 2007/0149924 to R. Marsh, the entire contents of both of which are hereby incorporated by reference.
Accordingly, a need exists for a hub protrusion having an increased surface area that contacts a patient's skin during an injection, thereby reducing the pressure exerted against the patient's skin during the injection.